MMA6281QR2 datasheet(5/12 Pages) FREESCALE

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Sensors

Freescale Semiconductor

MMA6281QT

BASIC CONNECTIONS

Pin Descriptions

Figure 4. Pinout Description

Figure 5. Accelerometer with Recommended

Connection Diagram

PCB Layout

Figure 6. Recommended PCB Layout for Interfacing

Accelerometer to Microcontroller

NOTES:

1. Use 0.1 µF capacitor on VDD to decouple the power

source. Do not exceed capacitor values of 2.2 or

3.3 µF. Slow dV/dt rise times on VDD may cause the

device to not power up below 0°C.To ensure

operation below 0°C ensure VDD line has the ability

to reach 2.2V in < 0.1 ms as measured on the device

at the VDD pin. If output signal does not assert itself,

then the dv/dt at the VDD pin of the device should be

measured.

2. Physical coupling distance of the accelerometer to

the microcontroller should be minimal.

3. The flag underneath the package is internally

connected to ground. It is not recommended for the

flag to be soldered down.

4. Place a ground plane beneath the accelerometer to

reduce noise, the ground plane should be attached to

all of the open ended terminals shown in Figure 6.

5. Use an RC filter with 1.0 kΩ and 0.1 µF on the

outputs of the accelerometer to minimize clock noise

(from the switched capacitor filter circuit).

6. PCB layout of power and ground should not couple

power supply noise.

7. Accelerometer and microcontroller should not be a

high current path.

8. A/D sampling rate and any external power supply

switching frequency should be selected such that

they do not interfere with the internal accelerometer

sampling frequency (11 kHz for the sampling

frequency). This will prevent aliasing errors.

9. PCB layout should not run traces or vias under the

QFN part. This could lead to ground shorting to the

accelerometer flag.

Table 4. Pin Descriptions

Pin No.

Pin Name

Description

g-Select1

Logic input pin to select g level.

g-Select2

Logic input pin to select g level.

3VDD

Power Supply Input

4VSS

Power Supply Ground

5 - 7

N/C

No internal connection.

Leave unconnected.

8 - 11

N/C

Unused for factory trim.

Leave unconnected.

Sleep Mode

Logic input pin to enable product or

Sleep Mode.

ZOUT

Z direction output voltage.

N/C

No internal connection.

Leave unconnected.

XOUT

X direction output voltage.

N/C

No internal connection.

Leave unconnected.

Top View

14 13

g-Select1

N/C

g-Select2

VDD

VSS

Sleep Mode

VDD

VSS

VDD

0.1 µF

XOUT

1 kΩ

Logic

Input

0.1 µF

ZOUT

1 kΩ

Logic

Inputs

g-Select2

g-Select1

MMA6281QT

POWER SUPPLY

VDD

VSS

Sleep Mode

g-Select1

g-Select2

XOUT

ZOUT

VDD

VSS

VRH

A/DIN

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